1. Field of the Invention
The invention relates to water-dissipatable, lipophilic polymers comprising pendant sulfonic acid salt groups, methods of making such water-dissipatable polymers and the use of such polymers in aqueous systems, including aqueous coating compositions.
2. Related Art
As used herein, xe2x80x9cwater-dissipatablexe2x80x9d, xe2x80x9cdissipated in waterxe2x80x9d, and other grammatical forms of such terms are meant to include all forms of one or more substances in water; that is, a solution and/or a colloidal system, including but not limited to solutions, dispersions, suspensions, emulsions, etc.
As used herein, xe2x80x9clipophilic polymersxe2x80x9d means polymers that are non-dissipatable, or substantially non-dissipatable in water. The polymer, however, may contain components, or be the polymerization product of monomers, which in and of themselves are water-dissipatable, as long as the polymer is not. Further, the term xe2x80x9cpolymerxe2x80x9d is intended to include oligomers unless otherwise stated. Any xe2x80x9clipopholic polymerxe2x80x9d is contemplated herein; however, in general, the lipophilic polymer possess an Mn in the range of about 300 to about 100,000, more preferably about 1000 to about 50,000 and especially about 1000 to about 20,000.
As used herein, xe2x80x9caqueous systemxe2x80x9d means a system wherein one or more substances are dissipated in water.
Organic carriers, solvents, emulsifiers, dispersing agents, etc. have historically been used to dissipate generally lipophilic polymers (sometimes also referred to as xe2x80x9cresinsxe2x80x9d) in coatings, adhesives, sealants, film forming products, etc. The desire to reduce the use of the above-mentioned organic carriers, solvents, etc. in polymer systems has lead to the search for alternatives. One of those is using water as the carrier for polymers ultimately dried, cured and/or reacted with other components to produce coatings, adhesives, sealants, etc. As noted, for example, in WO-A-92/07010, various options have been pursued to dissipate in water otherwise water-incompatible lipophilic polymers in order to form stable aqueous systems.
EP-A-543228 (U.S. Pat. No. 5,336,711) discloses, in part, an aqueous binder composition wherein a polyisocyanate component is emulsified in an aqueous solution or dispersion of water-dilutable organic polyols containing at least one polyester resin having carboxylate and hydroxyl groups and grafted with vinyl monomers. That patent publication also teaches preparation of carboxylate groups by at least partially neutralizing carboxyl groups with a base, preferably ammonia or dimethyl ethanol amine. However, if such aqueous organic polyol systems are used with polyisoyanates the presence of organic amines can catalyze the undesired reaction between water and isocyanate. This produces carbon dioxide which can foam, leading to undesirable effects, such as imperfections in a coating layer. Aqueous organic polyol systems requiring little or no organic amine are therefore desirable. Further, if such aqueous organic polyol systems are used in coating compositions comprising aminoplasts, such organic amines can retard the curing reaction of the polyol and the aminoplast.
Aqueous systems of organic polyols having sulfonate groups are generally known from, for example, EP-A-537568 (U.S. Pat. No. 5,344,873) and EP-A-542105 (U.S. Pat. No. 5,331,039). EP-A-537568 discloses generally an aqueous binder composition containing (A) an aqueous solution or dispersion of a water-dilutable organic polyol component containing at least one water-dilutable polyester resin requiring, among other things, 4 to 70 milliequivalent sulfonate groups per 100 g polyester resin, and (B) a polyisocyanate component emulsified in the aqueous solution or dispersion (A). EP-A-537568 prefers sulfonate groups that are obtained from aromatic sulfocarboxylic acids having a molecular weight of 224 to 360. Also among the sulfonate groups specifically mentioned as suitable synthesis components are sulfonate diols such as those described in DE-OS-2 446 440 (U.S. Pat. No. 4,108,814). However, the sulfonate diols disclosed there are difficult to prepare.
Difunctional monomers containing a xe2x80x94SO3M group attached to an aromatic nucleus wherein M is hydrogen or a metal ion are known from U.S. Pat. No. 4,973,656. Use in polyester water-dissipated resins is also disclosed. There is, however, little flexibility in the configuration of the compounds disclosed in U.S. Pat. No. 4,973,656, and thus insufficient capability to adapt the compounds to various systems and situations.
EP-A-542105 may be summarized as disclosing a water-based binder composition wherein a polyisocyanate component is emulsified in an aqueous solution or dispersion of a water-dilutable organic polyol component which is a mixture of at least 5 wt. % of each of at least two hydroxy-functional polymers selected from a group of five classes or types of resins, designated as A1 through A5 in EP-A-542105. Among the hydroxy-functional polymers possible in A1 through A5 are polyester resins having sulfonate groups (A3 and A4) and acrylate-grafted polyester resins having sulfonate groups (A5). In addition to the inconvenience and cost of preparing and/or obtaining two polyols, the binder compositions of EP-A-542105 also risk incompatibility and/or colloidal instability due to the presence of two of the polyols mentioned in that publication.
Consequently, the search for water-dissipatable polymers are sought which overcome these and other problems found with current technology.
In one embodiment, the current invention relates to lipophilic polymers having pendant sulfonic acid salt groups of the following formula (Formula 1) 
wherein
R1 is selected from the group (a) hydrogen, (b) C1 to C20 alkyl, (c) substituted C1 to C20 alkyl and (d) the following formula (Formula 2) 
xe2x80x83wherein R3 and R4 are independently selected from the group hydrogen and methyl, and
X is the residue of a monoepoxy-containing compound,
R2 is selected from the group C1 to C6 alkylene and C1 to C6 substituted alkylene, and
M is a cation.
In a specific variation of this embodiment the lipophilic polymers further comprise pendant C1 to C4 alkoxy polyalkoxy alkylene groups.
In a preferred embodiment of the current invention the lipophilic polymer is a polyol, preferably an addition polymer polyol.
Another embodiment of the current invention comprises an at least partially unsaturated polymer to which has been grafted an addition polymer of the above-described type.
The invention also comprises methods of preparing the above-described polymers.
The invention further comprises aqueous systems, and in particular aqueous coating compositions comprising the above-described polymers wherein the polymers serve as binders, emulsifying agents and/or dispersing agents.
According to the present invention, the xe2x80x9clipophilic polymerxe2x80x9d may be based upon any number of the well-known variety of polymer systems. As examples thereof may be mentioned polyesters and alkyds, polyepoxyesters, polyethers, polyurethanes, cellulose-based polymers, polycarbonates, polyacrylates, polyvinyls, polyamides, polyacetals, etc.
Preferably, the polymers contain essentially ester and/or addition polymer linkages such as, for example, polyesters (including alkyds), polyepoxyesters and polymers produced via free-radical addition polymerization. These preferred polymers may also contain minor amounts of other types of linkages such as, for example, urethane (e.g., from chain extension of a polyol with a diisocyanate), ether (e.g., chain extension of a polyol with a diepoxide) and others well-known to those skilled in the relevant art. Further, if the lipophilic polymers are grafted with an addition polymer comprising sulfonic acid salt groups, the lipophilic polymer must be at least partially unsaturated to enable grafting of the addition polymer. The compositions of a number of suitable lipophilic polymers are also discussed in further detail below.
As noted above, addition polymers according to the current invention are a preferred embodiment; more particularly, addition polymer polyols. Addition polymer polyols, in general; that is, polyols formed by addition polymerization of monomers, are well-known to those skilled in the art and need not be described in detail here. All such addition polymers are suitable for use in the current invention. Non-limiting examples of free-radically polymerizable monomers suitable for producing addition polymers of the invention are (cyclo)alkyl (meth)acrylates having one to about 12, preferably about 1 to about 6, carbon atoms in the (cyclo)alkyl group, such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isobornyl (meth)acrylate, dodecyl (meth)acrylate and cyclohexyl (meth)acrylate; (cyclo)alkyl esters of dicarboxylic acids with one to about 12, preferably about 1 to about 6 carbon atoms in the (cyclo)alkyl groups, such as dimethyl maleate and diethyl maleate; alkoxy polyalkoxy alkylene (meth)acrylates, such as methoxy polyethylene glycol (meth)acrylates (also referred to as xe2x80x9cMPEG (meth)acrylatesxe2x80x9d, typically having a molecular weight from about 300 to about 2000); other (meth)acrylates with ether groups, such as 2-methoxy-ethyl methacrylate, 2-ethoxy-ethyl methacrylate and 3-methoxy-propyl (meth)acrylate; hydroxyalkyl (meth)acrylates, such as 2-hydroxy ethyl (meth)acrylate, 2-hydroxy propyl (meth)acrylate, 4-hydroxy butyl acrylate, 6-hydroxy hexyl acrylate, p-hydroxy polypropylene glycol (meth)acrylate, and alkoxy derivatives thereof; monovinyl aromatic compounds, such as styrene, vinyl toluene, xcex1-methyl styrene and vinyl napthalene; other substituted (meth)acrylic compounds such as (meth)acrylamide, (meth)acrylonitrile, N-methylol (meth)acrylamide and N-alkyl (meth)acrylamides; other mono unsaturated compounds such vinyl chloride, vinyl acetate, vinyl propionate and vinyl pyrrolidone; and unsaturated monoepoxides, such as glycidyl (meth)acrylate and glycidyl allyl ether.
Monomers suitable for providing pendant sulfonic acid salt groups of Formula 1 generally are free-radically polymerizable monomers having at least one terminal group of Formula 1. Non-limiting examples of such monomers are styrene sulfonic acid, 2-acrylamido-2-methyl-propane sulfonic acid, amino ethane sulfonic acid and the salts of such acids, and sodium dodecyl allyl sulfosucciante. Other examples of these monomers are monomers which are the reaction product of (a) free-radically polymerizable monomers having an isocyanate group, for non-limiting example, dimethyl-m-isopropenyl benzyl isocyanate, and isocyanato-ethyl methacrylate, and (b) alkali metal taurinates (in particular, sodium taurinate), salts of N-(alkyl)taurinates (especially the sodium salts thereof), and adducts comprising the reaction product of monoepoxy-containing compounds and alkali metal taurinates, in particular sodium taurinates. Regarding such adducts, reference is made to Formula 2 above. xe2x80x9cXxe2x80x9d in Formula 2 is determined by the monoepoxy-containing compound selected to react with alkali metal taurinates. Examples of such compounds are given below.
In principle, any monoepoxy-containing compound is suitable for preparation of the above-described adduct of taurinate and monoepoxy-containing compound. Particularly suitable epoxy-containing compounds are mono glycidyl ethers, such as alkyl glycidyl ethers, for example, butyl glycidyl ether and 2-ethylhexyl glycidyl ether; mono glycidyl esters, including glycidyl esters of carboxylic acids, for example, glycidyl esters of xcex1, xcex1-dimethyl octanoic acid (available under the trademark Cardura(copyright) E from Shell Chemical Corporation, Houston, Tex., the glycidyl ester of Versatic acid (available as Cardura(copyright) E-10 from Shell Chemical Corporation, Houston, Tex.), etc. In one method of preparing such adducts the reactants are brought together in mixtures of water and organic solvent, preferably, water-miscible solvents, for non-limiting example, the water-miscible solvents mentioned below for addition polymerization, and particularly, methoxy ethanol, methoxy propanol and ethanol. The ratio of monoepoxy-containing compound to the monomer supplying sulfonic acid or sulfonic acid salt depends on the polymer to which the adduct is ultimately attached and the use made of that polymer (e.g., reactive polyol, emulsifier, dispersing agent, etc.). However, generally, a suitable ratio is about 0.8 to 1.6, preferably about 1 to about 1.4.
Pendant, nonionic stabilizing moieties can be provided by copolymerization with other monomers during polymer formation. For example, such pendant nonionic groups may be provided to addition polymers by monomers comprising both unsaturated groups capable of addition polymerization and one or more nonionic groups, such as alkoxy polyalkoxy alkylene (meth)acrylate, preferably the so-called xe2x80x9cMPEG-(meth)acrylatesxe2x80x9d in molecular weight ranges of about 350 to about 2000. Other nonionic monomers which may be copolymerized during addition polymerization are the reaction products of dimethyl-m-isopropenyl benzyl isocyanate and either polyether amines or adducts which are the reaction product of polyether amine and a monoepoxide. Polyether amines (also referred to as alkoxy polyalkoxy alkylene monoamines) can be prepared by polymerization of monoalcohol with ethylene oxide (EO), propylene oxide (PO) or mixtures of EO and PO. The polymerization is carried out in the presence of an initiator such as methanol. After polymerization the end-group is converted to an amine by conventional methods. Polyether amines are commercially available as Jeffamine(copyright) M from Huntsman Corporation, Zaventem, Belgium.
Pendant nonionic groups may also be provided by grafting onto an already formed polymer backbone via appropriate reactive groups before, simultaneously, or after modification with the sulfonate adduct. The already discussed polyether amines and their adducts prepared from the reaction product of polyther amine and a monoepoxide are perferably used.
Methods for preparing addition polymers, and in particular addition polymer polyols, are well-known to the skilled artisan. Accordingly such polymerization need not be described in detail here but will be discussed in general terms.
Addition polymerization reactions are usually carried out under inert atmosphere (e.g., nitrogen). Polymerization temperatures are generally from about 60xc2x0 C. to about 200xc2x0 C., preferably about 100xc2x0 C. to about 160xc2x0 C. at atmospheric pressure. Reaction at elevated pressure (typically about 1.5 to about 10 bar) is also possible. The reaction is also conducted in the presence of a radical initiator. A non-limiting list of suitable radical initiators includes dibenzoyl peroxide, dicumyl peroxide, t-butyl-2-ethyl hexanoate, t-butyl perbenzoate, t-butyl cumyl peroxide, methyl ethyl ketone peroxide, di-t-butyl peroxy-3,5,5-trimethyl cyclohexane, di-t-butyl peroxide, 1,3-bis(t-butyl)peroxy isopropyl benzene and mixtures thereof. The radical initiators are typically used in amounts from about 0.05 wt. % to about 10 wt. %, perferably from about 1 wt. % to about 5 wt. %, based on the weight of the monomer mixture. Optionally, chain regulators may be used, such as for non-limiting example, n-octyl mercaptan, dodecyl mercaptan and alkyl mercapto propionates, such as butyl mercapto propionate.
Addition polymerization reactions preferably take place in about 5 to about 30 wt. % organic solvent, preferably water-miscible organic solvent. Non-limiting examples are glycol ethers and propylene glycol ether, such as methoxy propanol, butyoxy ethanol, isopropoxy propanol, n-propoxy propanol, diethylene glycol mono-and di-methyl ether and dipropylene glycol mono-and di-methyl ether. Small amounts (e.g., less than about 10-20 wt. %) non-water-miscible organic solvents may also be used. Larger amounts of non-water-miscible solvents may also be used but they typically require removal, e.g. by standard distillation techniques.
Various processes can be used to carry out addition polymerization. For non-limiting example, one homogeneous monomer mixture can be reacted, the monomers and/or monomer mixtures can be sequentially dosed and reacted, some or all monomers can be continuously introduced while varying the concentration of such monomers (see generally, for example, the process disclosed in U.S. Pat. No. 3,804,481), etc.
In one embodiment of the current invention, an addition polymer comprising sulfonate adducts and optionally nonionic adducts are grafted to an at least partially unsaturated polymer, preferably an at least partially unsaturated polyester. However, other at least partially unsaturated polymers can be used, for non-limiting example, polyepoxyester, polyether, polyurethane, etc. and mixtures thereof. In a preferred embodiment, the at least partially unsaturated polymers are polymer polyols. In a particularly preferred embodiment, the at least partially unsaturated polymer is a polyester polyol.
The preparation of polyols, and especially polyester polyols, is well-known (see, for example, Surface Coatings, S. Paul, John Wiley and Sons, 1985) and need not be described in detail here. Generally, polyester can be prepared from aliphatic, cycloaliphatic or aromatic monocarboxylic acids, for non-limiting example, benzoic acid, t-butyl benzoic acid, saturated fatty acids (such as isononanoic acid), 2-ethyl hexanoic acid, unsaturated fatty acids (such as soya fatty acid, dehydrated castor oil fatty acid, sorbic acid, etc.) and mixtures; polycarboxylic acids, their esters and anydrides, for non-limiting example, hexahydrophthalic acid, isophthalic acid, phthalic acid, maleic acid, terephthalic acid, itaconic acid, adipic acid, dimer fatty acids, trimellitic acid, pyromellitic acid and mixtures; aliphatic, cycloaliphatic or araliphatic monofunctional alcohols, for nonlimiting example, decanol, n-hexanol, cyclohexanol and mixtures; hydroxy carboxylic acids, for non-limiting example, dimethylol propionic acid, castor oil fatty acid, hydroxy caproic acid and mixtures; and polyols, for non- limiting example, ethylene glycol, propane diol-1,2, neopentyl glycol, butane diol, trimethylol propane, trimethylol ethane, 1,4-cyclohexane dimethanol, glycerol, pentaerythritol, di-trimethylol propane, di-pentaerythritol and mixtures.
Polyesters useful in the current invention can be prepared by well-known processes, for non-limiting example, the melt process or the azeotropic process. If necessary or desirable, a catalyst can be employed. Reaction temperature is typically about 150xc2x0 C. to about 250xc2x0 C. If transesterification is involved, produced alcohol is typically removed (e.g., methanol when dimethyl terephthalate is employed).
An unsaturated site for grafting can be provided, in principle, by any copolymerizable monomer having unsaturation. Particularly preferred unsaturated monomers are maleic anhydride, itaconic acid and unsaturated fatty acids, in particular, conjugated unsaturated fatty acids. Unsaturation may also be provided after polymer formation by an unsaturated monoisocyanate, for non-limiting example, dimethyl-m-isopropenylbenzyl isocyanate. A polyester polyol grafted with an addition polyol can be prepared by free-radical addition polymerization in the presence of an at least partly unsaturated polyol. The free-radical addition polymerization can be carried out according to the methods described above.
A polymer of the current invention comprising pendant sulfonic acid salt groups, and optionally pendant nonionic groups, is readily dissipatable in an aqueous medium by conventional means, e.g. stirring, high shear, etc. If the polymer is an organic polyol, it is preferably dissipated at temperatures between about 50xc2x0 C. and about 100xc2x0 C. Typically, an aqueous dispersion made according to the current invention comprises a solids content of from about 30 wt. % to about 60 wt. %, preferably from about 35 wt. % to about 55 wt. %.
Sulfonic acid salt groups of the current invention need to be present in amounts sufficient to render the lipophilic polymer water-dissipatable. The amount of sulfonic acid salt groups necessary will vary with the type of lipophilic polymer, but is readily determined by a skilled artisan based on the hydrophobic character of the polymer and the further teachings found herein.
One preferred embodiment of the current invention is an addition polymer polyol which comprises pendant sulfonic acid salt groups, perferably about 0.01 to about 0.4 meq/g sulfonic acid salt groups, most preferably about 0.07 to about 0.25 meq/g and, optionally, nonionic stabilizing groups, the nonionic stabilizing groups preferably 0.01 to about 10 wt. %, most preferably about 0.5 to about 3 wt. % of the polyol. Such an addition polymer polyol typically has a molecular weight of about 100 to about 50,000 preferably about 100 to about 40,000, more preferably about 1000 to about 20,000, most preferably, about 1000 to about 10,000 and an OH number of about 20 to about 300. The nonionic stabilizing groups are typically alkoxy polyalkoxy alkylene groups, preferably having 1 to 4 carbon atoms per group.
Another perferred embodiment comprises an organic polyol comprising an at least partially unsaturated polyol having a molecular weight of about 300 to about 3000, an OH number of about 20 to about 300 and an acid number of less than 5 which has been grafted with an addition polymer polyol having an molecular weight of about 1000 to about 50,000 preferably about 100 to about 40,000, more preferably about 1000 to about 20,000, most preferably about 1000 to about 10,000 and an OH number of about 20 to 300. The organic polyol further comprises about 0.01 to about 0.4 meq/g sulfonic acid salt groups, most preferably about 0.01 to about 0.25 meq/g and, optionally nonionic stabilizing groups, the nonionic stabilizing groups preferably being 0.1 to about 10 wt. %, most preferably about 0.5 to about 3 wt. % (based on solids) of the organic polyol. The nonionic stabilizing groups are typically alkoxy polyalkoxy alkylene groups, preferably having 1 to 4 carbon atoms per group.
A preferred use of aqueous systems according to the current invention is in coating compositions. One particularly preferred coating composition comprises a polyol according to the instant invention and a curing agent for the hydroxyl groups of the polyol. Such hydroxyl-reactive curing agents are well-known in the art and need not be fully described here. Preferred classes of hydroxyl-reactive curing agents are N-methylol-containing aminoplasts, N-methylol ether-containing aminoplasts and polyisocyanates, more particularly, water-dispersible isocyanates and blocked isocyanates (blocked, e.g., with methyl ethyl ketoxime.)
Particularly preferred aminoplasts are methylol melamines comprising about 4 to about 6 methylol groups per molecule, wherein at least about 3 of the methylol groups have been etherified with methanol, butanol and/or a methanol or butanol condensation product of formaldehyde and N,Nxe2x80x2-ethylene diurea. The preferred ratio of hydroxyl groups provided by the polyol to hydroxyl-reactive groups in the aminoplast is about 0.7 to about 1.5.
Water-dispersable polyisocyanates are well-known and need not be described here in detail. Water-dispersible polyisocyanates particularly suitable for use in the current invention include, but are not limited to tolylene diisocyanate (TDI), 4,4xe2x80x2-diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HMDI), 1-isocyanate-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (IPDI), bis-(isocyanatocyclohexyl)methane, etc. The ratio of hydroxyl groups provided by the polyol to hydroxyl-reactive groups of the polyisocyanate is typically about 0.5 to about 5, preferably about 0.9 to about 2.
The coating compositions of the current invention can further comprise other components and additives conventionally present in coating compositions, for non-limiting example, pigments, coloring agents, pigment dispersing agents, thixotropic and other rheological agents, accelerators (e.g., tin catalysts, p-toluene sulfonic acid and blocked derivatives thereof, etc.).
The coating compositions can be applied to any substrate; that is, wood, metal, plastic and other synthetic materials, etc. Further, the aqueous dispersions of the instant invention can be employed in all types of coating compositions particularly, paints. They are especially useful as clear coats and pigmented top coats for metal surfaces (particularly automotive and transportation vehicle coatings and more particularly refinishing). These applications make use of the fact that the current invention provides stable, aqueous coating compositions (typically xe2x80x9cpaintsxe2x80x9d) which, when cured, provide high quality coatings. These coatings have high aesthetic qualities (e.g. high gloss ( greater than 70 at 200) and lack of haziness) without sacrificing technical characteristics, such as hardness, solvent resistance and water resistance. They are thus particularly suitable for coatings that are xe2x80x9cfinishesxe2x80x9d; that is, visible coatings that must provide aesthetic appeal, such as clear coats and pigmented top coats on vehicles, appliances, etc. and indeed, any consumer product.
Any known methods for applying coating compositions can also be used. Non-limiting examples of such application methods are spreading (e.g. brushing, rolling, by paint pad or doctor blade), spraying (e.g., airfed spray, airless spray, hot spray and electrostatic spray), flow coating (e.g. dipping, curtain coating, roller coating and reverse roller coating) and electrodeposition. (See generally, Paint and Surface Coatings: Theory and Practice, R. Lambourne, Editor, Ellis Horwood, 1987, page 39 et seq.) Coating compositions of the instant invention can be formulated to accommodate drying and curing at ambient temperature and elevated temperature (e.g. about 60xc2x0 C. to about 160xc2x0 C.).
In addition to being used as the binder or resin component in a coating composition, the polymers of the current invention can also be employed in aqueous systems, particularly coating compositions, as a polymeric emulsifying agent or dispersing agent for other polymers in the aqueous system, especially those which do not have sulfonate and/or nonionic groups. The other polymer present in the aqueous system is typically a polyol, for non-limiting example, polyester polyol, polyepoxyester polyol, polyether polyol, polyurethane polyol, polyacrylate polyol, etc. and mixtures thereof. However, the polymers of the current invention can also be used as an emulsifying and/or dispersing agent for other polymers, such as alkyds. Polymers of the current invention can also be used as a dispersing agent for pigments.
The invention is further described and illustrated by the examples which follow.